International Journal of Recycling of Organic Waste in Agriculture (IJROWA) Feasibility of mango by-products and biogas solid residue aerobic co-composting at different C/N ratios Volume 13 (2024) IJROWA Issue 1, January 2024 2023 11 17 Feasibility of mango by-products and biogas solid residue aerobic co-composting at different C/N ratios 10.57647/j.ijrowa.2024.1301.02 EN Do Thi My Phuong Department of Environmental Engineering, College of the Environment and Natural Resources, Can Tho University, Can Tho 900000, Vietnam 0009-0000-5777-8751 Le Hoang Viet Department of Environmental Engineering, College of the Environment and Natural Resources, Can Tho University, Can Tho, Vietnam Nguyen Thuy Duong Department of Environmental Engineering, College of the Environment and Natural Resources, Can Tho University, Can Tho, Vietnam Nguyen Xuan Loc Department of Environmental Science, College of the Environment and Natural Resources, Can Tho University, Can Tho 900000, Vietnam 0000-0003-0423-6179 Journal Article 2023 11 17 Purpose: Co-composting of mango by-products and biogas solid residue eliminates some shortcomings of composting these wastes separately. Specifically, co-composing solves the problem of the low pH values in mango by-products while enhances biodegradable organic matter of biogas solid residues. However, no research report is available on co-composting of mango by-products (MB) and biogas solid residue (BR). Method: This study established three in-vessel lab-scale composting bins with 3 different C/N ratios, including Bin 1: 27.4/1 (156 kg MB + 144 kg BR); Bin 2: 30.23/1 (193 kg MB + 107 kg BR); and Bin 3: 37.7/1 (224 kg MB + 76 kg BR). The raw compost materials underwent 57 days of incubation, including 36 days of raw incubation and 21 days of mineralization. Results: Bin 3 containing larger amounts of mango by-products and less amounts of biogas residue showed a higher percentage of remaining carbon in the final products (17.97%), lower nitrogen loss (17%), and showed 0.5% increase in available P2O5 content, compared to the other bins. From 300 kg of initial raw material, the final compost mass in Bin 1, Bin 2, and Bin 3 were 26.2 kg, 32.7 kg, and 88.1 kg, respectively. Conclusion: Resultantly, an initial C/N ratio of 37.7/1 could be suggested in the aerobic co-composting of biogas residue with mango by-products.   Research Highlights ·       Co-composting of mango by-products and biogas solid residue eliminates some of the weaknesses of composting these wastes separately. ·       The incubation period determined was 57 days of incubation, including 36 days of raw incubation and 21 days of mineralization. ·       Among three C/N ratios surveyed, the highest C/N in bin 3 (C/N=37.7/1) showed the best-favoured condition for mango by-products treatment and generate the highest amount of compost product. ·       Bin 3 showed the highest percentage of remaining carbon in compost products (17.97%), a lower in nitrogen loss (17%), and 0.5% increase in available P2O5 content.